Lamp



June 7,1927. 1,631,610

.W. H. WOOD LAMP Filed June 20, 1924 Patented June 7, 1927.

UNITED STATES WILLIAM H. WOOD, OF SOUTH EUCLID, OHIO.

LAMP.

Application filed June 20, 1924. Serial No. 721,148.

This invention relates to lamps and has particular reference to those lamps which are used as headlights for vehicles, such as automobiles, trucks, motor boats, and other land and water craft where it is desirable to keep all the reflected rays below a given line in order to prevent the creation of a glare which might dazzle or confuse men or draft anim'als moving in the opposite direction, and this without loss of light or dimunition of its intensity. The object of the invention is the provision of a light controlling device which shall throw a relatively concentrated beam directly forward for distant lighting, together with a downwardly diffused light nearer at hand, while restraining all the rays to and below a horizontal plane, and all this with a minimum of regard to the position of the light source; the provision of a reflector that will produce a satisfactory and legal driving light without focussing and without requiring any special glasses, lenses, shields, or other lightkilling contrivances; while further objects and advantages of the invention will appear as the description proceeds.

It is a known optical property of a paraboloid reflector that every ray of light arising at its focal point will be reflected forwardly in strict parallelism with the paraboloid axis forming a cylindrical pencil of light; that if the source be moved along the axis to a point forward of the focal point the reflector rays will be converged; and that if the source be moved along the axis to a point rearward of the focal point, the reflector rays will be diverged. No practical light source is known which approximates a geometrical point in size, wherefore the light from any known source when reflected from a true paraboloid reflector must necessarily contain some glaring rays, either the upwardly divergin rays produced when the source is wholly ehind focus or the upwardly converging rays produced when the source is wholly ahead of focus or some of both when the light source traverses the focal point. In addition the lateral projection of portions of the light source produces a complicated cross-fire of rays, some of which exhibit a glaring tendency.

The lare produced witha plain paraboloid refh'sctor 1s least when the light source is located at some one point therein and the process of finding that point is popularly known as focus'sing. This is an operation of some difficulty and'is required not only in the case of a plain reflector but also when special lenses are employed since most of these are designed to give the best results only when used with a properly focussed light source. I have discovered, however, that if the light source be displayed a material distance above the reflector axis and the glaring portions of the reflector be then so modified as to overcome the glare, a substantially increased tolerance is secured as regards the position of the bulb longitudinally of the reflector.

The principle of my invention will be made clearby reference to the accol'npanying drawings wherein Figs. 1, 2 and 3 are diagrammatic views of the same paraboloid re- ,flector showing the result of moving the light source to different positions therein; F1g. 4 is a diagrammatic view of a composite reflector embodying m improvements; Fig. 5 is'a sectional view of a headlight equipped with an improved reflector; Fig. 6 is a front elevation of the reflector shown in Fig. 5.

In Figs. 1, 2, and 3, A represents a parabola, aa its major axis, gg its parameter, 7' its focal point, and s a light source of point-size.

In Fig. 1 this source is moved to a point on the parameter above. the axis; obviously all rays which fall upon the reflector along the parameter gg are reflected parallel to the axis as shown at p. 12; all rays which fall on the upper half of the reflector behind the parameter are converged downwardly as indicated at q, by reason of the fact that they originate, or seem to ori inate, in front of the focal point; and afi rays which fall on the upper half of the reflcctor in front of the parameter are diverged upwardly as indicated at 1', by reason of the fact that they originate, or seem to originate, behind the focal point.

In Fig. 2 this source is located in front of.

the parameter as well as above the axis; all rays falling upon the reflector along the line wa: which contains both the source and the focal pointwill be reflected forwardly arallel to the axis as indicated at p. p; al rays falling upon the reflector as if they originated ahead of the focal point are converged as at g. g; and all rays falling upon the reflector as if they originated behind the focal oint are diverged as indicated at 1'. 7*.

In Fig. 3 this sourceis located behind the parameter as well as above the axis; all rays focal point are diverged as indicated at 1".

r. In the case of diverging rays only those are objectionable in causing glare which originate at the top of the reflector as indicated at r, and in the case of converging rays only those are objectionable in causing glare which originate at the bottom of the reflector as shown at 9.

Comparison of these three diagrams will show that the glaring rays arise solely inthe regions L and M, the heel portion of the reflector being free from offense at all times; and the width of these glare-producing regions depends upon the displacement of the source. Accordingly in order to overcome this glare it is only necessary to lean the glare producing portions downwardly as indicated at B and D in Fig. 4; This can be effected either by leaning the axis of the portion in question, or by employing a different portion of a coaxial parabola or some other curve. It is suflicient, also, to restrict these modified portions solely to the region shown, although I prefer to modify the whole of the bottom half of the reflector in order to secure certain other advantages in addition, namely the concentration of certain of the rays for distant lighting.

In the particular embodiment shown in Fig. 4, the lower half of the reflector consists of a semi-paraboloid C having its axis cc, slightly inclined downwardly, and in addition is shown'asslightly larger than the upper paraboloid A, but t e focal points are preferably arranged one substantially above the other so that when the paraboloids are of unequal size the heel of they lower is offset behind that of the upper as shown at a. In case the leaning of the portion B is effected by inclining its axis 6, I prefer to locate the focal point f thereof in the same vertical line with the points 7; and f but this is not imperative, since a much similar leaning can be effected by moving the focal oint f rearwardly. R8878 from a source falling thereon are re ected toward the axis aa as shown at It is also, sometimes, desirable further to modify the bottom half of the reflector so as to obtain a more exact control of the light and. one such modification will now be described, although others can be used in connection with the top-half arrangements I have outlined, or they may be entirely omitted. Applying the method of analysis heretofore employed, it will be seen that all 'rays'from the point S passing through the point f will be reflected as shown at 25 parallel to the axis cc and, therefore, inclined downwardly with relation to the axis a-a; all rays passing behind the point 7 will be diverged yet more downwardly as shown at u; and those passing ahead of the point 7" will be converged so that at some line, perhaps that indicated at o, the reflected rays become parallel with the axis a-a as shown at w. However, if the lower half of the reflector be a true paraboloid, all'rays falling ahead of this point will be reflected above this axis which may be considered as sub stantially horizontal although in some cases it may be slightly inclined for added caution) and hence produce an objectionable glare. In order to overcome this possibility, 1 preferably give an additional ,lean to the forward strip of this lower half, as indicated at D. The main advantage of this refinement is that it affords a greater range of permissible movement to the light source; have shown it as a parabola upon the axis d-d with focal point at 7'. All rays falling thereon are deflected downwardly as shown at h.. It will be noted upon further analysis that as the point S is moved toward or from the reflector throughout a considerable range none of the reflected rays will rise above the axis a-a. Although first one regionand then another will concentrate the light in a parallel beam, the other regions will always deflect the light downwardly relatively thereto and no portion of the light will produce glare.

When all these features are combined in a practical reflector, the same appears as shown in Figs; 5 and 6, wherein A, B, C and D represent the regions heretofore described. At the sides these various regions l'nerge with the side wings EE which are so inclined as to obviate all side glare as patented in and by my former Patents Nos. 1,235,274 and 1,235,275. These separate regions merge together so smoothly that the device can be drawn with no greater difliculty and polished with no greater expense than any plain paraboloid reflector.

All the reflector segments have their axes 1n the same vertical plane and their focal points in the same'vertical region, while the light source is located in the same plane and intersecting such focal region. The correction of the surface to compensate for this displacement includes the correction for most other displacements also, especially that in a fore and aft direction, and, to a smaller degree, that in a lateral direction.

However, the greater the vertical displacement of the light source the more diflicult it becomes to maintain any part of the beam arallel and this feature is indispensable or distant lighting, thus practically limit ing the permissible elevation. As an example, I have used w1th success a vertical displacement of the light source of 1/4 inch, the portion A having a focal length of-24/32 inch, the portion C having a focal length of 25/32 inch, and an inclination of 1 in 16 and the portions B and D being leaned sufficiently to compensate for this vertical displacement throughout a longitudinal move-- ment of the filament equal to twice its length or approximately l/ lth inch. Of course these figures are merely illustrative and not limiting.

The heel of the reflector is formed with a hole Z for the lamp socket 7 and I preferably solder the same rigidly therein, thus avoiding all the expense and complexity of focussing arrangements, dispensing with ex pensive types of sockets, and avoiding all necessity of aligning the front and rear of the reflector with any designated points of the housing. In case the segment be offset behind the segment A as shown in Fig. 4, the socket hole includes the shoulder G, thus preventing any abrupt shoulder, although the surfaces above and below that hole may be out of line as shown in Fig. 5. The corrections herein described compensate for all ordinary wabbling of the bulb, all ordinary variations between different bulbs, and all ordinary excess in the size of the filament above a geometricalpoint; for example the horizontal V-sl'iaped filament; although even this gives a better light if held vertically.

. Accordingly it becomes possible to use interchangeably all types of lamps, whether V-filament, round filament, or bar filament, and the same may be set either vertical or horizontal or at any oblique position.

When the socket 7 is ri idly connected to the reflector it is impossib le for the lamp to become mis-focussed, the manufacture of the lamp becomes a mere mechanical proposition, except for the reflector itself, the solid electrical contact affords a better and steadier light, all wabbling and misplacement of the socket are prevented, and the rear of the reflector is made air-tight, thus decreasing its tendency to tarnish and enabling the use of a cheaper housing. The lamp construction shown in Fig. 5 comprises a hollow sheet metal housing 1, having inturned fingers 2, adapted to receive the rim 3, and a movable ring 4, to secure both the glass pane 5, and the reflector, the latter not needing to be fastened'in any other way except a pin and slot or similar device to prevent rotation. The electric terminals pass freely through an openin 6 in the housing since the only pur-' pose o the latter is to protect the reflector from becoming dented or deformed.

While I have shown in Fig. 4 an arrangement wherein the source is located ahead of the parameter, it will be understood that I am not restricted thereto, although it is necessary to-modify some of the corrections applied to the various surfaces. Practically it u is possible to move some portion of the filament past the parameter with either set of modifications, although it isnecessary to remain for themost part upon that side for which the device is designed.

It will be understood that these various modifications :are so interrelated that it is necessary where one is varied that all be changed, if the ,same distribution of light is desired. In the preferred case the arrangement is such that some part of the reflector is always casting a horizontal beam for distant lighting, this part changing as the posi-. tion of the source is varied. In the example here shown, referring to Fig. 4;, if the source be started at the parameter the distance beam arises from the final portion of the region A, and all the other portions deflect downwardly. As the source is moved forward the rays from A are depressed and those from the portion D become horizontal,

1. In a lamp, a concave one piece sheet [metal reflector located with its main axis substantially horizontal, and a light source located therein and displaced above such axis, the upper heel portion of said reflector conforming substantially to a parabola whose axis coincideswith the first named axis, the portions of said; reflector adjacent its mouth and forward of said light source consisting of paraboloid segments leaned downwardly as regards the paraboloid surface defined b said heel portion, and the focal points 0 said sections all located in the region of the parameter of the paraboloid surface defined by said heel portion.

2. A one piece sheet metal reflector for headlights having that portion of its vertical section which lies above and adjacent to 'its axis a parabola coaxial with such main axis; and having that portion of its vertical section which lies below such axis and behind the parameter of such first parabola conforming to a arabola of. greater focal length than said rst parabola; and having that portion of its vertical section which lies below the first axis and ahead of said second parabola conforming to a third parabola whose axis is inclined downwardl relative to the axis of said second parabo-a.

3. In a lamp, 0. reflector having a:;;;pair.of,ll0

opposed semi-paraboloid portions located above and below a substantially common axis, in combination with a light source located abovesuch axis, one of said portions terminating approximately at its parameter and the other at a point behind its parameter, and additional paraboloid surfaces in front of said first surfaces and merging therewith and leaned downwardly relatively thereto, the relation of such surfaces to said source being such that throughout a considerable range of adjustment some one of said surfaces shall cast aconcentrated beam approximately parallel to said common axis 5 and the remaining surfaces shall cast their beams below the same.

4. In a headlight lamp, a rbflector whose vertical axial section exhibits a parabolic portion at and above the lamp axis and coaxial with such axis, a second parabolic portion on the opposite side of saidaxis from said first portion and having its axis diverging from said first axis, said Second portion terminating approximately at the parameter of the first parabola, and a segment of a third parabola in front of said second parabola and leaned downwardly relatively thereto. 1

5. In a lamp, a reflector, having a substantially horizontal axis and a plurality of paraboloid reflector sections grouped around said axis, all having their axes in a single vertical plane, there being above said first axis a substantially semi-paraboloid segment whose axis coincides substantially with said first axis, a pair of inclined side portions located in the same horizontal plane with said first axis, one at each side of the reflector, there being also a second paraboloid segment below said axis and facing the first mentioned segment, said second segment terminating approximately at the parameter of the first mentioned segment, and a paraboloid portion in front of and merging with the second segment and having its axis diverging downwardly from the axis of said second segment.

Intestimony whereof, I hereunto aflix my signature.

' WILLIAM H. WOOD. 

